URGENT: VMDKs residing on vSAN 6.6 and later that have been extended may encounter data inconsistencies [RESOLVED]

Last week VMware published a KB 58715 reporting virtual machine disks residing on vSAN 6.6 and later that have been extended may encounter data inconsistencies. For those who subscribed to VMware email communications, the following message has been sent recently.

vSAN66-Issue-01

As stated in the article, this issue might happen in a rare occurrence. Still, VMware encourages their clients to check the value of the advanced setting VSAN.ClomEnableInplaceExpansion on all ESXi hosts that are part of the vSAN cluster. If it is set to the default value of “1”, the vendor recommends changing it to “0” immediately. This can be done using the following PowerCLI command:

Foreach ($VMHost in (Get-Cluster -Name (Read-Host “Cluster Name”) | Get-VMHost)) {Get-AdvancedSetting -Entity $VMHost -Name VSAN.ClomEnableInplaceExpansion | Where-Object {$_.Value -ne ‘0’} | Set-AdvancedSetting -Value ‘0’ -Confirm:$false}

Fortunately, no reboot or service restart is required for this change to take effect, and it will become effective within 60 seconds.

It is good to see how much effort the vendor put into supporting vSAN and proactively inform users about any problems. Great service, VMware!

04/10/2018 – Update 1: VMware has realeased patches for both vSAN 6.6 and 6.7 that remediate this issue. Please read the resolution section in KB 58715 for more information.

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